The present invention relates to apparatus for packaging and dispensing a volatile substance to be dispensed in a vapor phase. In particular, it relates to apparatus for dispensing air fresheners, aromatizing agents, deodorizers, odor maskents, insect repellents, animal repellents, pheromones and combinations thereof.
Numerous vapor releasing devices have been described in the literature and manufactured heretofore. In some, the vaporizable substance is incorporated in a solid carrier medium from which it gradually evaporates and enters the atmosphere once a protective wrap or enclosure is breached or removed. In others, the substance is packaged in liquid form and vaporized in some manner to discharge into the atmosphere. It is with this latter type that the present invention closely relates.
In particular, a type of room freshener is known wherein an aromatic liquid is packaged in a container provided with a wick immersed in the liquid and communicating with a porous member having a broad evaporation promoting surface. Unfortunately, the pores of the wicking material and the porous member tend to clog while the surface of the porous member tends to discolor rendering the device both less effective and unattractive. In addition, the presence of liquid on the exterior surface creates a number of problems since the liquid can be an irritant if carried to the eyes of an individual, the liquid can be gotten on clothes, and can otherwise cause undesirable soiling.
Certain of the prior art devices have employed microporous membranes. Thus in Van Loveren et al. U.S. Pat. No. 4,387,849 there is described a hollow container comprising a shell which is at least partially porous, containing an entrapped volatile substance. The substance is entrapped in a gel and is, in the alternative, a perfume composition, a deodorant composition, an air freshener composition, an insecticide composition, a herbicide composition, an odor masking composition, a pheromone composition, an animal repellent composition, or an insect repellent composition. The container containing the entrapped volatile substance ceases to discharge into the atmosphere when placed in an outer air-tight container. Said patent refers to various microporous polymers giving as examples a polypropylene and filler composition, a polyurethane and filler composition, a composition of polyvinyl alcohol and xanthan gum, and a cyclodextrin and activated silicate composition. The patent also mentions production of a microporous film by heating a mixture of synthetic thermoplastic polymer which may be a polymer or a copolymer of an ethylenically unsaturated monomer, condensation polymer, polyphenylene oxide or a blend thereof and a compatible liquid to a temperature and for a time sufficient to form a homogeneous solution, allowing the solution to assume a desired shape and cooling the solution to initiate liquid-liquid phase separation followed by cooling to solidify the film.
The Van Loveren patent also describes a number of structural embodiments. The embodiment illustrated in its FIGS. 5 and 7, for example, takes the form of a right circular cylinder with microporous walls and containing the fragrance bearing gel which cylinder is packaged in an outer vial provided with a screw cap top. While the entire side wall of the cylinder is illustrated as microporous, the patent states that not all of the side wall need be so fabricated. Instead, merely the upper third or the upper quarter or the lower quarter of the side wall or even the top or the bottom of the cylindrical container may be fabricated from microporous polymer, the remainder of the cylinder shell being fabricated using a transparent substance which is rigid or flexible or using a silicate or quartz glass.
Experience with all of the microporous membranes mentioned in the Van Loveren et al. patent indicates that a captivating medium such as the disclosed gels is essential to prevent the volatile substance from wetting the outer surface of the microporous membrane and even forming droplets on the outer surface. This can stain and damage anything that comes in contact with it.